Gasolines containing polymeric additive agents



" proved gasolines olines employed heretofore.

United States 3,058,818 GASOLINES CONTAINING POLYMERIC ADDITIVE AGENTS Adlai E. Michaels, Cranford, Elbert D. Nostrand, Westfield, and Thomas S. Tutwiler, Watchung, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Apr. 22, 1959, Ser. No. 807,987 Claims. (Cl. 44-62) The present invention relates to improvements in the properties of petroleum distillate fuels. It more particularly relates to gasolines which have been improved by the incorporation therein of certain polymeric additive agents which effect a significant reduction in the amount of de.- posits, sludge and varnish formed in gasoline engines operated upon such fuels.

A primary factor in formation of deposits, sludge and varnish in gasoline engines is incomplete combustion of the fuels introduced into the combustion chambers of such engines. Studies carried out with radioactive tracer materials have shown that certain polynuclear aromatics and other relatively high boiling compounds normally found in gasolines are only partially burned under normal operating conditions. The small but significant quantities of hydrocarbons which remain unburned apparently undergo complex cracking, polymerization, and oxidation reactions in the combustion chamber and form carbonaceous deposits which adhere to the upper part of the cylinder head, the valves, the piston tops and other surfaces with which the hot gases come in contact. Some of these complex reaction products are also apparently blown past the piston rings into the crankcase of the engine where they are dissolved in the lubricating oil. When the oil subsequently comes into contact with hot metal surfaces, the dissolved materials apparently further react to form insoluble products which appear as sludge.

The effects of deposits, sludge and varnish thus formed in gasoline engines are serious ones. Residues accumulated in the combustion chambers are in part responsible for surface ignition, spark plug fouling, rumble, octane requirement increase and other combustion difliculties Well known to those skilled in the art. Material accumulated elsewhere in the engine often causes malfunctioning of the engine lubricating system, accelerates the rate at which wear of engine parts occurs, increases engine oil consumption, and results in improper valve and piston ring operation. All of these difficulties produce serious losses in engine power. Engine maintenance expense and engine life are also seriously affected.

The present invention provides a class of new and imwhich are much less susceptible to the formation of engine deposits, sludge and varnish than gas- -In accordance with the invention, it has now been found that the use of certain selected copolymers of vinyl pyrrolidones and esters of acrylic acids in gasolines greatly improves engine cleanliness, permits economies in engine operation generally unattainable heretofore, and obviates the necessity for certain costly refining process steps which were often necessary in the past in order to produce gasolines with the required cleanliness properties.

The copolymers which are employed as gasoline additives in order to reduce the formation of engine deposits, sludge and varnish in accordance with the invention are copolymers of N-vinyl pyrrolidones and alkyl esters of acrylic and methacrylic acids. Although the mechanism by which these copolymers act to reduce the formation of deposits, sludge and varnish in gasoline engines is not fully understood, it has been found that these particular copolymers possess properties not found in other copoly- Patented Oct. 16, 1962 mers of similar structure which have in the past been employed as additives in lubricating oils and similar compositions.

The N-vinyl pyrrolidones which constitute one monomer of the copolymers employed as gasoline additives in accordance with the invention are compounds having the following general formula:

OH=OH1 R N Rfl o0 R- --OR it it Where the Rs represent hydrogen atoms or aliphatic hydrocarbon radicals containing from 1 to 5 carbon atoms each.

Specific examples of such N-vinyl pyrrolidones include N-vinyl pyrrolidone itself, 3'methyl-l-vinyl-pyrrolidone, 4- methyl-l-vinyl-pyrrolidone, S-methyl-l-vinyl-pyrrolidone, 3-ethyl-l-vinyl-pyrrolidone, 4-ethyl-l-vinyl-pyrrolidone, 3, 3-dimethy1-l-vinyl-pyrrolidone, 3,4-dimethyl-1-viny1-pyrrolidone, 3,5-dimethyl-l-vinyl pyrrolidone, 5 ,S-dimethyl-lvinyl-pyrrolidone, 3,4-dipropyl-l-vinyl-pyrrolidone, 3,4,5- triisopropyl-l-vinyl-pyrrolidone, 3,4-dimethyl-5-propyl-lvinyl-pyrrolidone, 4-butyl-l-vinyl-pyrrolidone, 3-amyl-3,5- dimethyl-l-vinyl-pyrrolidone, 3,4,5 triethyl 3 butyl-lvinyl pyrollidone, 5,5-diamyl-l-vinyl-pyrrolidone and the like. N-vinyl pyrrolidone itself is particularly effective in preparing the copolymers utilized in accordance with the invention and is therefore preferred.

Acrylic esters employed as the second constituent of the copolymers are alkyl esters of acrylic and methacrylic acids having esterifying groups containing from 1 to about 24 carbon atoms. Alkyl esters in which the alkyl groups contain from about 4 to about 18 carbon atoms are particularly useful because of the solubility properties which they impart to the copolymers, and are therefore preferred for purposes of the invention. Examples of such esters which may be employed to prepare the copolymers include butyl methacrylate, n-hexyl methacrylate, dodecyl methacrylate, hexadecyl methacrylate, octadecyl acrylate, eicosyl methacrylate, Z-ethyl-hexyl acrylate, stearyl methacrylate, cetyl acrylate, and the like.

Esters of acrylic and methacrylic acids prepared from commercial mixed alcohols may also be used in preparing the copolymers employed in accordance with the invention. Such mixed alcohols include those prepared by the hydrogenation of coconut oil and marketed commercially under the trade name Lorol. One such mixture of alcohols consists primarily of lauryl alcohols but contains compounds of from about 10 to about 18 carbon atoms per molecule. This particular Lorol alcohol normally contains about 4.0% of C alcohol, about 55.5% of C alcohol, about 22.5% of C alcohol, about 14.0% of C alcohol, and about 4.0% of C alcohol. Tallow alcohol is a similar mixed product consisting primarily of cetyl and stearyl alcohols derived from tallow fat by hydrogenation. Other mixed alcohols available commercially are derived from soybean oil, cottonseed oil, and similar natural products and also have chain lengths within the range recited above which render them suitable for purposes 'of the invention.

A still further class of alcohols which may be employed in preparing the esters used as monomers in accordance with the invention are the 0x0 alcohols which are derived by the oxonation and hydrogenation of olefin polymers. A variety of alcohols may be produced by this method, depending upon the particular olefins employed. If a C copolymer of propylene and butylene oxo alcohol is produced.

is used, for example, C Typically C oxo alcohol consists of 29% of 3,5-dimethyl hexanol, 25% of 4,5-dimethylhexanol, 17% of 3,4-dimethylhexanol, 16% of 4-methyl-heptanol and S-methylheptanol, 2.3% of 4-ethyl-hexanol, 1.4% of 5,5-dimethylhexanol, 4.3% of 2-alkyl-alkynols, and 5% of other alcohols. If a propylene tetramer is subjected to oxonation and subsequent hydrogenation, a C oxo alcohol is produced. This higher alcohol consists of a mixture of alcohols similar to the C oxo alcohol mixture. Other alcohols of different chain lengths and different degrees of branching may be produced in similar manner. All of these alcohols are suitable for use in forming the esters employed as one of the monomers of the additives of the invention.

The alkyl acrylates and methacrylates and the N-vinyl pyrrolidones described in the preceding paragraphs are polymerized to produce the copolymers employed in gasolines in accordance with the invention by mixing them in proportions of from about 1 to about 30 Weight percent of the N-vinyl pyrrolidone and about 70 to about 99 Weight percent of the acrylate or methacrylate ester. Polymerization of the monomers in ratios of from about 5 to about 15 wt. percent of the N-vinyl pyrrolidone and about 85 to about 95 wt. percent of the acrylate or methacrylate ester is preferred. The polymerization reaction may be carried out without diluent or instead may be carried out in a solution of a parafiinic solvent such as heptane or white oil at a temperature in the range of from about 60 F. to about 250 F. Gamma radiation may be used topromote polymerization or instead a peroxide type catalyst such as benzoyl peroxide, a hydro peroxide or an azo catalyst such as a-a'azo-bis-isobutyronitrile may be employed. It is usually preferred to carry out the polymerization reaction under a blanket of an inert gas such as nitrogen or carbon dioxide in order to exclude oxygen. The polymerization time may vary from about 1 to about 36 hours.

The copolymers produced in the manner described above, may have molecular Weights in the range of from about 1000 to about 100,000 or higher Staudinger. It is generally preferred to limit the polymerization reaction so that a product having a molecular weight of from about 2000 to about 20,000 Staudinger is obtained. The copolymer product may be recovered from the polymerization reaction mixture by evaporating off the solvent.

The copolymer thus prepared may be incorporated in the gasolines in concentrations in the range of from about 0.001% to about 2.0% by weight. Concentrations in the range of from about 0.005% to about 0.2% are generally highly effective and are therefore preferred. An effective method for incorporating the copolymers in the gasolines is to employ a solvent such as xylene, a highly refined lubricating oil, a white oil or the like. The copolymers are soluble is gasolines at the concentrations in which they are used in accordance with the invention, however, and hence may be added directly to the fuel without the necessity for using any solvent at all.

The gasolines in which the copolymers are employed in order to reduce the formation of deposits, sludge and varnish are conventional fuels employed in internal combustion engines operating on the Otto cycle. They are supplied in a number of different grades depending upon the type of service for which they are intended. The copolymers may be employed in all of these grades but are particularly useful in motor gasolines. Motor gasolines as referred to in connection with the present invention are defined by ASTM Specification D439-56T in Types A, B and C. They are composed of a mixture of various types of hydrocarbons including aromatics, olefins, paraffins, isoparafiins, naphthenes and, occasionally, diolefins. They are derived from petroleum crude oil by refining processes such as fractional distillation, catalytic cracking, hydroforming, alkylation, isomerization, polymerization and solvent extraction. Motor gasolines normally have boiling ranges between about 70 F.

and about 450 F. The copolymers may also be em ployed in aviation gasolines, which have properties similar to those of motor gasolines but normally have somewhat higher octane numbers and narrower boiling ranges. The properties of aviation gasolines are set forth in US. Military Specification MIL-F-5572.

The copolymeric additives employed in accordance with the invention may be used in gasolines with other additive agents conventionally used in such fuels. It is conventional practice to employ from about 2 to about 4.6 cos. of tetraethyl lead, tetramethyl lead, dimethyldiethyl lead or a similar alkyl lead anti-knock agent in both motor gasolines and in aviation gasolines. Halogenated hydrocarbons and phosphorus compounds are generally employed as scavenger agents in gasolines containing lead anti-knock agents and are used in concentrations ranging from about 0.05 to about 1.0 or more theories of the phosphorus compound and from about 1 to about 3.0 theories of the halogenated hydrocarbons, based on the stoichiometric equivalent of the lead content. Other gasoline additives with which the additives of the invention may be employed include materials designed to stabilize tetraethyl lead and similar anti-knock agents, solvent oils, rust and corrosion inhibitors, antiicing agents, dyes and dye stabilizers. The additive agents employed in accordance with the invention are non-reactive in gasolines and may be used in conjunction with a wide variety of such conventional gasoline additives.

The nature and objects of the present invention are further illustrated by the results of tests carried out to demonstrate the effectiveness of the copolymeric additives in reducing the formation of sludge, varnish and deposits in gasoline engines. The copolymer employed in the test was a copolymer containing 8 wt. percent of N-vinyl pyrrolidone and 92 wt. percent of a rniXture of alkyl methacrylates having an average chain length of 9 /2 carbon atoms. The mixed alkyl methacrylate contained equal proportions of butyl methacrylates, C -C straight chain methacrylates, Lorol methacrylate, and tallow methacrylate. The copolymer had a molecular Weight of about 15,000 Staudinger. It was employed as a 38 wt. percent solution in mineral oil.

Two hundredths of 1% of the mineral oil containing 38 Wt. percent of the copolymer described above was incorporated into a commercial leaded gasoline to give a copolymer concentration of 0.0076 wt. percent. The gasoline used had the following properties:

Base Gasoline Inspections ASTM distillation, method D86:

Initial boiling point, F 90 10% boiling point, F 131 50% boiling point, F 231 90% boiling point, "F 362 Final boiling point, "F 424 Reid vapor pressure, p.s.i 13.5 General Motors gum, mg./ ml 3.2 ASTM breakdown time, min 845 FIA analysis:

Vol. percent saturates 67.1 Vol. percent olefins 16.3 Vol. percent aromatics 16.6 Tetraethyl lead, cc./gal 2.95 Research octane No 92.5 Motor octane No 85.5

Chevrolet engine attached to a dynamometer on a test stand was operated to the following repeated cycles for a period of about hours.

Test Conditions Jacket Oil Cycle Water Sump Intake Brake Air/ Dura- Cycle R.p.m. Outlet 'Iemp., Air, H. P. Fuel tion, Temp, F. F. Ratio Hrs.

At the conclusion of the 110 hour period, the engine was inspected and various parts were rated for sludge, deposits and varnish on a demerit scale ranging from 0 to 100, 0 indicating the presence of no deposits at all and 100 signifying that the particular part rated had the maximum amount of deposits it was capable of holding. The results of these ratings are set forth in the following table.

Demerit Ratings Base Gaso- Base Gasoline (Av. line+ 0.0076 of 2 Runs) Wt. Percent Copolymer Piston Skirt Varnish, Overall 79.0 40. 8 Thru Side 79. 5 45.0 Anti-Thrust S1de 78.3 36. 7 Ring Zone, OveralL. 14. 4 12.8 Sludge, Overall 6.9 5.0 Cylinder Head Top- 5.0 5. 0 Becker Arm Assembly 3. 7 5.0 Rocker Arm Cover.... 7. 5 2. 5 Crankshaft 6. 2 7. 5 Timing Gear Cover- 12.5 5.0 Push Rod Chamber 5.0 7. 5 Push Rod Chamber Coven. 11.2 7. 5 Crankcase 0 0 1 Copolymer A was a copolymer of 8 wt. percent N-vinyl pyrrolidone and 92 wt. percent of a mixture of alkyl methacrylates having alkyl groups averaging 9% carbon atoms in length, 38 Wt. percent in mineral oil.

The test results shown in the above table clearly demonstrate that the presence of the copolymer greatly improved the engine performance characteristics of the gasoline. Despite the very low concentration of copolymer used, the sludge and varnish produced when the engine was operated on the fuel containing the copolymer were significantly lower than those obtained when the base gasoline was used. It was further'observed that the use of the copolymer gave rise to no spark plug fouling difliculties whatsoever, although spark plugs normally become fouled very readily during the idle cycle of the test. Moreover, the carburetor and other parts of the fuel system were exceptionally clean when the copolymer additive was used, indicating that the copolymer was not. deposited out in the carburetor or elsewhere. It was also observed that use of the copolymer reduced engine oil consumption and gave increased power due to better valve operation. These improved results obtained with the copolymeric additive are particularly surprising in view of the fact that the polymers are essentially nonvolatile and must enter the combustion chamber of the engine by entrainment in the liquid phase rather than by vaporization.

Additional tests were carried out to determine the effect of the copolymers in other gasolines and at higher concentrations. The copolymer of N-vinyl pyrrolidone and mixed alkyl methacrylates previously described was added as a 38% solution in mineral oil to two leaded gasoline, one a commercial gasoline of regular grade and the other a specially blended gasoline of regular grade volatility known to result in the formation of much more deposits, sludge and varnish than are obtained with commercial fuels. The solution containing the copolymer was added to each gasoline in 0.04 wt. percent concentration, giving a copolymer concentration of 0.015 wt. percent in each fuel. Parallel tests were then carried out using the 6 gasolines thus prepared and the base gasolines containin no copolymer. The test conditions and procedures employed were the same as those described above. The results of these tests are shown in the following table.

Demerit Ratings i Base Base Gasoline Gasoline Base A+0.015 Base B+0.015 Gasoline Wt. per- Gasoline Wt. per- A 1 cent Co- B 4 cent 00- polymer polymer A a A 3 Piston Skirt Varnish, Over- 55.6 44. 9 87. 5 34. 6 65.0 51. 6 91. 7 36. 7 Anti-Thrust Si 48. 3 38. 3 83. 3 32. 5 Ring Zone, OveralL 12.1 10.1 18. 5 12.3 Sludge, Overall 4.2 0.3 8. 9 1.9

Cylinder Head Top 2. 5 0 5. 0 0 Rocker Arm Assembly..- 2. 5 0 5. 0 0 Rocker Arm Cover 5.0 O 7. 5 2. 5 Crankshaft 2. 5 0 7. 5 0 Timing Gear Cover 10.0 0 15. 0 2. 5 Push Rod Chamber 2. 5 0 15.0 0 Push Rod Chamber Cover 10.0 0 12. 5 5.0 Grankcase 2. 5 0 10. 0 5.0 Oil Screen 0 0 2.5 0

1 Rating indicates amount of sludge, deposits and varnish on part rated 0 signifying that the part was clean and 100 indicating that the part had the maximum amount of sludge, deposits and varnish it was capable of holding.

2 Base gasoline A was a regular grade leaded gasoline marketed commercially for use in automobiles.

3 Copolymer A was a copolymer of 8 wt. percent of N-vinyl pyrrolidone and 92 wt. percent of mixed alkyl methacrylates having mixed alkyl gfimps averaging 9% carbon atoms in length, 38 wt. percent in mineral o 4' Base gasoline B was a specially blended gasoline having the same volatility as gasoline A but much less clean-burning than gasoline A.

The data in the above table again demonstrate that gasolines containing the copolymers greatly improve engine cleanliness. The improvement was striking in the case of both gasolines, indicating that the eifect is not limited to any particular fuel.

It will be understood that the copolymer composition employed in the foregoing tests is merely representative of the copolymers useful as gasoline additives in accordance with the invention and that other copolymers previously described herein are similarly useful. Examples of such other copolymers are those having the compositions and molecular weights set forth below.

Monomers in Copolymer Staudinger M01. Wt.

10 Wt. Percent N-Vinyl Pyrrolidone Wt. Percent Lauryl Methacrylate 2, 500 5 Wt. Percent 3-Methyl-1-V' yl Pyrrolidone Wt.

Percent Decyl Acrylate 3, 500 15 Wt. Percent 5,5-Dimethyl-1-Vinyl Pyrrolidone 85 Wt.

Percent Tallow Methacrylate 20,000 17 Wt. Percent 3-Ethyl-1-Vinyl Pyrrolidone 83 Wt. Percent C -Oxo Methacrylate 18,000 21 Wt. Percent 5-Butyl-1-Vinyl Pyrrolidone 79 Wt. Percent n-Hexyl Acrylate 32,000 30 Wt. Percent 3,4-Dimethy1-l-Vlnyl Pyrrolidone 70 Wt.

Percent Ola-0x0 Acrylate 64,000 8 Wt. Percent N-Vinyl Pyrroli one 92 Wt. Percent Lorol 1 Methacrylate 4, 200 19 Wt. Percent 3,4,5-Trimethyl-1-Vinyl Pyrrolidone 81 Wt. Percent Dodecyl Acrylate 19,000 24 Wt. Percent 3-Amyl-1-Vinyl Pyrrolidone 76 Wt.

Percent 2-Ethyl Hexyl Acrylate 7, 000

20 Wt. Percent N-Vinyl Pyrrolidone i o'w'ffbifii' Stearyl Methacrylate 10, 000 25 Wt. Percent 3,3-Dimethyl-t-Butyl-1-Vinyl Py'rrolidone 75 Wt. Percent Soya Methacrylate 16,000 13 Wt. Percent 3 3-Dimethyl-4,4 DiethylJ-Vinyl Pyrrolidone 87 Wt. ercent Nonyl Acry ate 21,000 9 Wt. Percent 3,4 5-Triethyl-1Vinyl Py'rrolidone 91 Wt.

Percent Methyl Methaorylate 3,000

1 Trade name for technical lauryl alcohol.

done wherein the alkyl groups have from 1 to carbon atoms and from about 70% to about 99% by weight of an ester selected from the group consisting of alkyl acrylates and methacrylates in which the esterifying alkyl groups contain from 1 to about 24 carbon atoms.

2. A gasoline as defined by claim 1 wherein said ester is an alkyl acrylate.

3. A gasoline as defined by claim 1 wherein the esterifying alkyl groups in said ester contain an average of from 4 to 18 carbon atoms.

4. A gasoline as defined by claim 1 wherein said copolymer is a copolymer from about 5 to about wt. percent of an N-vinyl pyrrolidone and from about 85 to 95 wt. percent of an alkyl methacrylate.

5. A gasoline as defined by claim 1 wherein said copolymer is a copolymer of N-vinyl pyrrolidone and a mixed alkyl methacrylate.

6. A gasoline to which has been added from about 0.001% to about 2.0% by weight of a gasoline-soluble copolymer of from about 1% to about by weight of N-vinyl pyrrolidone selected from the group consisting of N-vinyl pyrrolidone and alkyl substituted N-vinyl pyrrolidone wherein the alkyl groups have from 1 to 5 carbon atoms and from about to about 99% by weight of an alkyl methacrylate wherein the alkyl groups contain from 1 to about 24 carbon atoms.

7. A gasoline as defined by claim 6 wherein said copolymer is present in a concentration of from about 0.005% to about 0.2% by weight.

8. A gasoline as defined by claim 6 wherein the alkyl groups in said alkyl methacrylate contain from about 4 to about 18 carbon atoms.

9. A gasoline as defined by claim 6 wherein said copolymer is a copolymer of from about 5 to about 15% of N-vinyl pyrrolidone and from about to '95 wt. percent of mixed alkyl methacrylates.

10. A gasoline as defined by claim 6 wherein said copolymer has a molecular weight between about 2000 and about 20,000 Staudinger.

References Cited in the file of this patent UNITED STATES PATENTS 2,800,452 Bondi et a1. July 23, 1957 2,866,729 Zimpel Dec. 30, 1958 2,892,690 Lowe et al. June 30, 1959 2,899,391 Mayhew et a1. Aug. 11, 1959 FOREIGN PATENTS 760,554 Great Britain Oct. 31, 1956 808,665 Great Britain Feb. 11, 1959 

1. A GASOLINE HAVING INCORPORATED THEREIN FROM ABOUT 0.001% TO ABOUT 2.0% BY WEIGHT OF A COPOLYMER OF FROM ABOUT 1% TO ABOUT 30% BY WEIGHT OF A COPOLYMER OF PYRROLIDONE SELECTED FROM THE GROUP CONSISTING OF NVINYL PYRROLIDONE AND ALKYL SUBSTITUTED N-VINYL PYRROLIDONE WHEREIN THE ALKYL GROUPS HAVE FROM 1 TO 5 CARBON ATOMS AND FROM ABOUT 70% TO ABOUT 99% BY WEIGHT OF AN ESTER SELECTED FROM THE GROUP CONSISTING OF ALKYL ACRYLATES AND METHACRYLATES IN WHICH THE ESTERIFYING ALKYL GROUPS CONTAIN FROM 1 TO ABOUT 24 CARBON ATOMS. 